(1) Class A: three per cent (3%) of his base earnings per annum plus five per cent (5%) of his excess earnings per annum.
(2) Class B: seven per cent (7%) of earned compensation, provided, that on July 1, 1967, or within four (4) months thereafter any class B member may elect to make additional contributions at the rate of seven per cent (7%) on that part of his earned compensation in excess of the maximum rate thereof, such contributions to be made on such compensation earned subsequent to July 1, 1967; and provided, further, that any member who has made such election or any member retiring between June 1, 1967 and June 30, 1967, may also elect to make an additional payment in a lump sum equal to the total of the contributions at seven per cent (7%) of that part of his earned compensation in the period from October 1, 1957 to June 30, 1967, which was in excess of the maximum rate thereof, plus interest from the date such compensation was received to the date such additional payment is made at the regular rate per annum compounded annually, such election and payment to be made on or before October 31, 1967.
(3) Class C: eleven and seventy-three hundredths per cent (11.73%).